Alekha C. Nayak — Page 2

arXiv2016

Vector dark matter annihilation with internal bremsstrahlung

We consider scenarios in which the annihilation of self-conjugate spin-1 dark matter to a Standard Model fermion-antifermion final state is chirality suppressed, but where this suppression can be lifted by the emission of an additional photon via internal bremsstrahlung. We find that this scenario can only arise if the initial dark matter state is polarized, which can occur in the context of self-interacting dark matter. In particular, this is possible if the dark matter pair forms a bound state that decays to its ground state before the constituents annihilate. We show that the shape of the resulting photon spectrum is the same as for self-conjugate spin-0 and spin-1/2 dark matter, but the normalization is less heavily suppressed in the limit of heavy mediators.

hep-ph↗

arXiv2015

ELKO fermions as dark matter candidates

We study the implications of the ELKO fermions as a cold dark matter candidate. Such fermions arise in theories that are not symmetric under the full Lorentz group. Although they do not carry electric charge, ELKOs can still couple to photons through a nonstandard interaction. They also couple to the Higgs but do not couple to other standard model particles. We impose limits on their coupling strength and the ELKO mass assuming that these particles give dominant contribution to the cosmological cold dark matter. We also determine limits imposed by the direct dark matter search experiments on the ELKO-photon and the ELKO-Higgs coupling. Furthermore we determine the limit imposed by the gamma ray bursts time delay observations on the ELKO-Higgs coupling. We find that astrophysical and cosmological considerations rule out the possibility that ELKO may contribute significantly as a cold dark matter candidate. The only allowed scenario in which it can contribute significantly as a dark matter candidate is that it was never in equilibrium with the cosmic plasma. We also obtain a relationship between the ELKO self-coupling and its mass by demanding it to be consistent with observations of dense cores in the galactic centers.

hep-ph↗